The tabular data tables in this product include detection frequency and benchmark exceedances of agricultural pesticides in surface water samples collected in rivers and streams. The data are a product of a national-scale assessment of the toxicity of 221 pesticides at 74 sites during water years 2013 - 2017 conducted by the U.S. Geological Survey National Water Quality Pesticide Monitoring Program. Data were collected to 1) determine where and how often pesticides are detected in surface waters, and 2) identify regions in the continental United States that had streams with a higher risk of potential pesticide toxicity by comparing concentrations to both aquatic-life and human-health benchmarks.

In 1991, the U.S. Geological Survey (USGS) began a study of more than 50 major river basins across the Nation as part of the National Water-Quality Assessment (NAWQA) project of the National Water-Quality Program. One of the major goals of the NAWQA project is to determine how water-quality conditions change over time. To support that goal, long-term consistent and comparable monitoring has been conducted on streams and rivers throughout the Nation. Outside of the NAWQA project, the USGS also has collected long-term water-quality data to support additional assessments of changing water-quality conditions. These data have been combined to provide insight into how natural features and human activities have contributed to water-quality changes over time in Nation’s streams and rivers. This USGS data release contains all of the input and output files necessary to reproduce the results from the SEAWAVE-Q pesticide models described in the associated U.S. Geological Survey Scientific Investigations Report. Data preparation for input to the model is also fully described in the above mentioned report.

In 1991, the U.S. Geological Survey (USGS) began a study of more than 50 major river basins across the Nation as part of the National Water-Quality Assessment (NAWQA) project of the National Water-Quality Program. One of the major goals of the NAWQA project is to determine how water-quality conditions change over time. To support that goal, long-term consistent and comparable monitoring has been conducted on streams and rivers throughout the Nation. Outside of the NAWQA project, the USGS also has collected long-term water-quality data to support additional assessments of changing water-quality conditions. These data have been combined to provide insight into how natural features and human activities have contributed to water-quality changes over time in Nation’s streams and rivers. This USGS data release contains all of the input and output files necessary to reproduce the results from the SEAWAVE-Q pesticide models described in the associated U.S. Geological Survey Scientific Investigations Report. Data preparation for input to the model is also fully described in the above mentioned report.

In 1991, the U.S. Geological Survey (USGS) began a study of more than 50 major river basins across the Nation as part of the National Water-Quality Assessment (NAWQA) project of the National Water-Quality Program. One of the major goals of the NAWQA project is to determine how water-quality conditions change over time. To support that goal, long-term consistent and comparable monitoring has been conducted on streams and rivers throughout the Nation. Outside of the NAWQA project, the USGS also has collected long-term water-quality data to support additional assessments of changing water-quality conditions. These data have been combined to provide insight into how natural features and human activities have contributed to water-quality changes over time in Nation’s streams and rivers. This USGS data release contains all of the input and output files necessary to reproduce the results from the SEAWAVE-Q pesticide models described in the associated U.S. Geological Survey Scientific Investigations Report. Data preparation for input to the model is also fully described in the above mentioned report.

This dataset consists of drainage basin boundaries for 212 U.S. Geological Survey (USGS) stream sites sampled in the National Water-Quality Assessment (NAWQA) Program, the National Stream Quality Accounting Network (NASQAN), and the National Monitoring Network (NMN). Of the 212 sites, 206 have either a contributing or total drainage basin boundary, and the remaining 6 have both a total drainage basin boundary and a smaller contributing basin boundary. Collectively, these 218 basin boundaries have been used in a geographic information system (GIS) to generate basin characteristics for the assessment of trends in concentrations of pesticides streams of the United States.

This data release is comprised of data tables of input variables for seawaveQ and surrogate models used to predict concentrations of select pesticides at six U.S. Geological Survey National Water Quality Network (NWQN) river sites (Fanno Creek at Durham, Oregon; White River at Hazleton, Indiana; Kansas River at DeSoto, Kansas; Little Arkansas River near Sedgwick, Kansas; Missouri River at Hermann, Missouri; Red River of the North at Grand Forks, North Dakota). Each data table includes discrete concentrations of one select pesticide (Atrazine, Azoxystrobin, Bentazon, Bromacil, Imidacloprid, Simazine, or Triclopyr) at one of the NWQN sites; daily mean streamflow; 30-day and 1-day flow anomalies; daily median values of pH and turbidity; daily mean values of dissolved oxygen, specific conductance, and water temperature; and 30-day and 1-day anomalies for pH, turbidity, dissolved oxygen, specific conductance, and water temperature. Two pesticides were modeled at each site with three types of regression models. Also included is a zip file with outputs from seawaveQ model summary. The processes for retrieving and preparing data for regression models followed those outlined in the SEAWAVE-Q R package documentation (Ryberg and Vecchia, 2013; Ryberg and York, 2020). The R package waterData (Ryberg and Vecchia, 2012) was used to import daily mean values for discharge and either daily mean or daily median values for continuous water-quality constituents directly into R depending on what data were available at each site. Pesticide concentration, streamflow, and surrogate data (continuously measured field parameters) were imported from and are available online from the USGS National Water Information System database (USGS, 2020). The waterData package was used to screen for missing daily mean discharge values (no missing values were found for the sites) and to calculate short-term (1 day) and mid-term (30 day) anomalies for flow and short-term anomalies (1 day) for each water-quality variable. A mid-term streamflow anomaly, for instance, is the deviation of concurrent daily streamflow from average conditions for the previous 30 days (Vecchia and others, 2008). Anomalies were calculated as additional potential model variables. Pesticide concentrations for select constituents from each site were pulled into R using the dataRetrieval package (De Cicco and others, 2018). Three of the six sites (Kansas River at DeSoto, Kansas; Missouri River at Hermann, Missouri; and White River at Hazleton, Indiana) pulled pesticide data for WY 2013–17 whereas the other three sites (Fanno Creek at Durham, Oregon; Little Arkansas River near Sedgwick, Kansas; and Red River of the North at Grand Forks, North Dakota) pulled pesticide data for WY 2013–18. Discrete pesticide data were matched with daily mean discharge and daily mean or median water-quality constituents and the associated calculated short-term (1-day) and mid-term (30-day) anomalies from the date of sampling. Pesticide concentrations were estimated using the SEAWAVE-Q (with surrogates) model using 19 combinations of surrogate variables (table 2 in the associated SIR, "Comparison of Surrogate Models to Estimate Pesticide Concentrations at Six U.S. Geological Survey National Water Quality Network Sites During Water Years 2013–18.") at each of 12 site-pesticide combinations (table 3 in the associated SIR). Three measures of model performance—the generalized coefficient of determination (R2), Akaike’s Information Criteria (AIC), and scale—were included in the output and used to select best-fit models (Table 4 of the associated SIR). The three to four best-fit SEAWAVE-Q (with surrogates) models with sample sizes at least five times the number of variables were selected for each site-pesticide combination based on generalized R2 values—the higher, the better. If generalized R2 values were the same, the model with the lower AIC value was used. The standard surrogate regression and base SEAWAVE-Q models were

Dissolved pesticides were measured in weekly water samples from 100 wadeable freshwater streams across eleven states in the Midwestern U.S. during May-August, 2013, as part of the Midwest Stream Quality Assessment study conducted by the U.S. Geological Survey's (USGS) National Water Quality Assessment (NAWQA) Project. Of the 100 stream sites, 12 were urban indicator sites and the remaining 88 sites were located along an agricultural gradient of watershed land use. Twelve depth- and width-integrated water samples were collected at each site within the 14-week study period. Water samples were filtered (0.7 micrometers) and analyzed for 227 pesticide compounds by direct-injection liquid chromatography with tandem mass-spectrometry, and for glyphosate by Enzyme-Linked Immunoassay in a separate analysis. Potential aquatic toxicity was evaluated using the Pesticide Toxicity Index and by comparison to U.S. Environmental Protection Agency aquatic-life benchmarks. This data release provides sampling site locations, method information, summaries of quality-control data, and concentration data for pesticide compounds in environmental weekly water samples, in support of the journal article, “Complex mixtures of dissolved pesticides show potential aquatic toxicity in a synoptic study of Midwestern U.S. streams,” by Nowell, L.H., Moran, P.W., Schmidt, T., Norman, J.E., Nakagaki, N., Shoda, M.E., Mahler, B.J., Van Metre, P.C., Stone, W.W., Sandstrom, M.W., and Hladik, M.L.